Bondable polyamide

ABSTRACT

Self-bondable polyamides are prepared by reacting an aromatic diisocyanate or diamine with a mixture of terephthalic acid and an aliphatic dibasic acid having at least 6 carbon atoms. These self-bondable amides can also be used as topcoats for wires having basecoats of another polymer, e.g. a polyester, polyester-imide, or polyamide-imide.

This is a division of application Ser. No. 311,385, filed Oct. 14, 1981,now U.S. Pat. No. 4,420,535.

BACKGROUND OF THE INVENTION

The present invention relates to a novel self bondable aromaticaliphatic polyamide.

An all-aromatic polyamide as made in accordance with Allard U.S. Pat.No. 3,642,715 does not exhibit self-bonding characteristics even whentested via the NEMA Bonding Test No. 57.1.1.2. at temperatures up to260° C. The all-aliphatic polyamides as described by the work of OtisU.S. Pat. No. 4,216,263 and Kawaguchi U.S. Pat. No. 4,163,826 arethermoplastic in nature and exhibit good bonding characteristics but donot offer the excellent humidity resistance and resistance to attack byrefrigerants as do the aromatic-aliphatic polyamides of the presentinvention.

Gilman U.S. Pat. No. 2,268,586 has a broad teaching of making polyamidesby reacting a dibasic acid with a diisocyanate but does not showself-bondable polyamides.

Onder U.S. Pat. No. 4,072,665 discloses a novel copolymer of the formula##STR1## where R is 60 to 85 percent of an aliphatic dibasic carboxylicacid with (CH₂)_(x) recurring units and x being an integer of 7 to 12inclusive, the remaining 15 to 40 percent of R being m-phenylene. Theproportions are indicated to be critical in Onder. Onder also indicateson column 6, lines 43-52 that a portion of the recurring units up to 10%can have R from a different dicarboxylic acid, e.g. terephthalic acid.Onder uses his products for many things including wire coatings, column6, lines 11-22. However, Onder makes no mention of a solution cast filmwhich is baked and yet retains self-sealing or adhesive properties.

SUMMARY OF THE INVENTION

There have now been prepared random aromatic-aliphatic copolyamideshaving the recurring unit ##STR2## where AL is the divalent hydrocarbonresidue of an unsubstituted aliphatic dicarboxylic acid having 6 to 36carbon atoms or more, usually ○AL is (CH₂)_(x) where x is 4 to 34,preferably 6 to 12, most preferably 10. Examples of such dicarboxylicacids include adipic acid, sebacic acid, azelaic acid and dodecanedioicacid. However, ○AL can be the residue of an unsaturated dicarboxylicacid, e.g. dimerized linoleic acid or dimerized oleic acid or dimerizedtall oil. R is tolylene, phenyl, ##STR3## where F is O, CH₂ or SO₂. Lesspreferably all or a part of R can be cycloaliphatic, e.g. cyclohexyleneor methylenedicyclohexyl, Ar is p-phenylene, y is 35 to 80% of therecurring units and z is 65 to 20% of the recurring units. Usually y is40 to 70% of the recurring units and preferably y is about 60 to 70%,most preferably 65% of the recurring units. If y is above 70% there is atendency to gel on standing.

The copolyamides can be prepared in conventional manner by reacting amixture of the dicarboxylic acids, e.g. dodecanoic acid and terephthalicacid with a diisocyanate, e.g. toluene diisocyanate or methylenediphenyldiisocyanate, or with the corresponding diamine, e.g. toluenediamine, 4,4'-methylene diphenyl diamine (methylene dianiline),oxydianiline, phenylene diamine, diaminodiphenyl sulfone, or a mixtureof such diisocyanates or of such diamines. As indicated there can alsobe employed a minor amount of 4,4'-methylene diphenyl diamine orcyclohexyl diamine. In reacting with the diamine rather than thediisocyanate it is of course possible to employ other acylating agentsthan the acid, e.g. there can be used the acyl halides, e.g. thedichloride or dibromide of dodecandioic acid or the lower alkyl esters,e.g. dimethyl dodecandioate, diethyl dodecandioate, and dibutyldodecanedioate.

Preferably in the formula R has the mole percent ratio of4-methyl-m-phenylene/2-methyl-m-phenylene/4,4'-methylene diphenylene inthe range of 40/10/50 to 80/20/0. The reaction is carried out in anamide solvent such as N-methyl-2-pyrrolidone (NMP).

The copolyamides of the invention are useful as a self-bonding coatingfor magnet wire. This coating is usually applied in an amide basedsolvent system, e.g., N-methyl pyrrolidone or a mixture of N-methylpyrrolidone and an aromatic hydrocarbon. The major advantages offered bythis novel enamel are:

(1) High temperature retention of bond strength.

(2) The quality of the base coat is not lessened, and in some cases, thequality of the base coat is improved by the bonding overcoat.

(3) The coating is resistant to attack by refrigerants.

(4) The coating has improved humidity resistance.

(5) The coating has improved chemical resistance.

(6) The coating is less costly than commercially available alternatives.

(7) The end user's cost is reduced by elimination of a costly secondaryinsulation.

(8) By eliminating the solvent-borne secondary insulation requirement,the bond coat offers obvious ecological advantages.

(9) Good adhesion to self-supporting high-temperature films.

Thus, the novel, self-bonding wire coating provides the magnet wire useran economical and ecological alternative with significant improvementsin bond strengths, hermetic resistance, and chemical resistance whencompared to other self-bond wire coatings. This novel coating alsooffers the motor manufacturer an option to eliminate secondaryinsulations as the self-bonding wire coating will produce resultsequivalent to or better than those achieved with the secondaryinsulations currently used.

It was previously pointed out that the copolyamides of the presentinvention are superior, in humidity resistance and resistance to attackby refrigerants, to the products of Otis U.S. Pat. No. 4,216,263. Thuswhen a sample of a polyamide as described in Otis is subjected to a 100percent humidity at 70° C., it exhibits an initial resistance of about370,000 megohms. After aging one week, the megohm resistance was about280,000 megohms; after two weeks, the resistance had dropped to about160,000 megohms. The aromatic-aliphatic polyamide of the presentinvention (based on Mondur TD-80, 4,4-methylene diphenylenediisocyanate,terephthalic acid and dodecanedioic acid), when submitted to this test,gave the following results:

    ______________________________________                                                     After        After                                               Initial      One Week     Two Weeks                                           ______________________________________                                        422,000 megohms                                                                            900,000 megohms                                                                            820,000 megohms                                     ______________________________________                                    

The dielectrics of the all-aliphatic polyamides of Otis were reduced by50 percent after two weeks at 100 percent relative humidity and 70° C.The aromatic-aliphatic polyamides of this invention, however, did notsignificantly change after the two-week aging. The all-aliphatic nylonsare true thermoplastics, unlike the aromatic-aliphatic polyamides of theinvention which, when initially bonded at 200° C., retain good bondstrength at 200° C. The aromatic-aliphatic polyamides of the invention,when coated over a polyester of the type described by Meyer in U.S. Pat.Nos. 3,201,276 and 3,211,585, will upgrade the base polyester to a NEMAClass 155° C. or greater magnet wire coating system. The entiredisclosure of the Meyer patents are hereby incorporated by reference andrelied upon. When coated over other wire enamels or wire enamel systems,the inherent properties of the coated wire are not adversely effected.The aliphatic-aromatic polyamides of this invention will self-bond attemperatures of 170° C. or greater when tested in accordance with NEMATest Specification 57.1.1.2 with resulting bond strengths of greaterthan seven pounds when broken at 180° C.

When this novel enamel is coated over a self-supporting,high-temperature film, such as a polyimide, polyparabanic acid,polyamide, or polyamide-imide film, then baked to dry, the film may thenbe self-bonded and will exhibit outstanding inner laminar adhesion.

If a polyamide, in 70/30 NMP/xylene, is made from 100% of an alkanedioicacid such as dodecanedioic acid and a mixture of toluene diisocyanateand methylene diphenyl diisocyanate, then the enamel product gels onstanding. In fact there is a tendency for gelation to occur if theamount of dodecanedioic acid goes above 70 mole percent and especiallyabove 78 mole percent based on the total of dodecanedioic acid andterephthalic acid.

Among the advantages of the copolyamides of the invention, in additionto or in amplification of those set forth above are:

(1) The wire coating is bondable at 200° C. and yet retains good bondstrength at 180° C. However, once the polymer is "Heat Set" above theapparent glass transition temperature of the aromatic-aliphaticpolyamide, the apparent glass transition temperature increases, thusgiving some thermoset properties to the coating.

(2) The aromatic-aliphatic polyamide system of the invention is the onlyamide bonding system offered which is not in part a physical blend of anall aliphatic amide such as Nylon 6;6,6; 11 or 12. Thearomatic-aliphatic polyamide is, however, an in situ reaction product ofan aromatic diacid and an aliphatic diacid, preferably with a blend ofaromatic diisocyanates to yield a random aromatic-aliphatic polymer. Thepreferred reactants are terephthalic acid and dodecanedioic acid withtoluene diisocyanate and methylenediphenyl diisocyanate in a 70:30 moleratio. The reaction is carried out in an amide-type solvent such asN-methyl-2-pyrrolidone.

(3) The aromatic-aliphatic polyamide, when coated over ISONEL 200,yields a Class 155° C. magnet wire; and, with the exception of the heatshock, displays Class 180° C. properties.

When coated over ISOMID, excellent properties as a Class 180° C. magnetwire are observed.

(4) The aromatic-aliphatic polyamide coated over ISONEL 200 pases the A.O. Smith Freon Blister Test; conventional Nylon 6,6 coated over ISONEL200 fails this test.

(5) The moisture resistance of the aromatic-aliphatic polyamide is alsosuperior to the Nylon 11 types.

(6) The aromatic-aliphatic polyamides offer a significant cost advantageover the systems based upon Nylon 11 or 12.

As indicated above the enamels of the invention exhibit good bondstrengths when coated over ISONEL 200 and ISOMID wire enamel. Thus whenbonded at 200° C. for 20 minutes they have shown bond strengths of 1 to6.2 lbs. and even up to 7.4 pounds at 180° C. without degrading otherwire properties by application of the bond coat.

The heat-bondable copolyamide film of the invention can be applied byconventional wire coating techniques to give a wire that may be woundinto coils, armatures, stators, etc., and heat bonded, therebyeliminating the need for an impregnating varnish, to give awire-insulation system of unusual thermal resistance. In the process ofeliminating the need for a varnish dip, the need for expensive dippingapparatus ovens, lengthy cure cycles, and high energy costs areeliminated.

The bondable copolyamide of the invention can be employed, for example,as a top coat over a wire having a base coat or coats of, for example:

1. a glycerine or other aliphatic polyhydric alcohol polyester, e.g.glycerine-ethylene glycol terephthalate polymer as in Precopio U.S. Pat.No. 2,936,296,

2. tris(2-hydroxyethyl)isocyanurate polyester, e.g.tris(2-hydroxyethyl)isocyanurate(THEIC)-ethylene glycol-terephthalatepolymer as in Meyer U.S. Pat. No. 3,342,780,

3. a polyester coated with an amide-imide polymer, e.g. the polyester ofPrecopio or Meyer U.S. Pat. No. 3,342,780 coated with an amide-imidepolymer as shown in Koerner U.S. Pat. No. 3,022,200 and Standard OilBritish Pat. No. 1,056,564.

4. a polyester-imide which is the reaction product of THEIC, ethyleneglycol, terephthalic acid (or isophthalic acid), methylene dianiline (oroxydianiline) and trimellitic anhydride, e.g. as in Meyer U.S. Pat. No.3,426,098. In place of THEIC, there can be used glycerine, e.g. as inthe polyester-imides of Schmidt U.S. Pat. No. 3,697,471. Likewise, therecan be used as the base coat the diethylene glycol or triethylene glycolmonoether modified polyester-imide resins of Keating U.S. Pat. No.4,119,608,

5. amide-imide coated polyester-imide as in the Keorner and Standard Oilpatents,

6. monolithic amide-imide as in the Standard Oil patent,

7. polyimide such as Pyre ML as in Edwards U.S. Pat. Nos. 3,179,634;3,179,630; 3,179,631; 3,179,632, and 3,179,633,

8. as a coating over an acrylic (acrylic-methacrylic acid ester) topcoated polyimide of the type of Lecton (DuPont),

9. conventional Formvar (polyvinyl formal), epoxy (e.g. bisphenolA-epichlorohydrin), urethane, and nylon top coated urethane. The entiredisclosures of the Meyer U.S. Pat. No. 3,342,780, Precopio, Koerner,Standard Oil, Keating, Meyer U.S. Pat. No. 3,426,098, and the Edwardspatents are hereby incorporated by reference and relied upon.

The wire enamels can be applied to either bare or base coated copper,aluminum, silver, or other wires using conventional coating proceduresand wire speeds, e.g., 30-150 ft/min. and curing the wire is carried outat conventional temperatures. The speed is adjusted according to wiresize and enamel to obtain optimum cure as is known in the art.

The copolyamides of the invention are also useful as bondable coatingsover film wrapped wire, e.g.

1. Kapton--a polyimide film of DuPont as in the Edwards patents

2. Nomex--a DuPont aromatic polyamide (isophthalic acid with an aromaticdiamine).

The copolyamides of the invention can be used as adhesives to apply overself-supporting films, e.g. used in printed circuit boards andcapacitors. Typical self-supported films include Kapton polyimide, Mylar(polyethylene terephthalate) polyester, Nomex, polytetrafluoroethyleneand perfluoroethylene-perfluoropropylene copolymer.

The copolyamides of the invention can be employed as cast films foradhesive use. The film is cast from solution and can then be used as anadhesive.

In film, strand or filament form the copolyamide can be used as asubstitute for Dacron in wrapped glass cloth. Dacron is not hightemperature resistant. Hence replacing the Dacron filaments by filamentsof the copolyamide of the invention gives higher temperature resistantproducts.

Nomex is available as cast or sheet insulation. The heat bondablecopolyamide of the invention can be used as a wrapping therefore to holdthe Nomex together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of bond strength vs. percent of aliphatic dibasic acid(dodecanedioic acid); and

FIG. 2 is a graph comparing the bond strength of the copolyamide withthat of Nylon 11.

The composition can comprise, consist essentially of, or consist of thematerials set forth.

EXAMPLE 1

This example is a working example of the present invention.

    ______________________________________                                                                 Load                                                 Raw Materials            in Grams                                             ______________________________________                                        (1) N--methyl-2-pyrrolidone                                                                            4168                                                 (2) Toluene diisocyanate (Mondur TD-80)*                                                               1033                                                 (3) 4,4' Methylene diphenyldiisocyanate                                                                 637                                                 (4) Terephthalic Acid     494                                                 (5) Dodecanedioic Acid   1267                                                 (6) Xylene               2243                                                 (7) N--methyl-2-pyrrolidone                                                                            1050                                                 ______________________________________                                         *Mondur TD80 is a 80/20 blend of 4methyl-m-phenylene diisocyanate and         2methyl-m-phenylene diisocyanate and is commercially available from Mobay     Chemical Company, Pittsburgh, PA.                                        

Parts one through three charged at room temperature into a 12-liter,round-bottom reaction flask, equipped with an agitator, a thermometer,an inert gas purge, and a water-cooled condenser fitted with a flexibletube which was immersed in a flask containing a mixture of water anddenatured ethyl alcohol. (The reaction by-products carried through thecondenser by the carbon dioxide and nitrogen are trapped in thewater-alcohol solution). Parts four and five were added at roomtemperature with agitation and a blanket of nitrogen was applied overthe reaction. The temperature was raised slowly by use of an electricheating mantel to approximately 75° C. when carbon dioxide evolutionbegan. The external heat was then reduced and the temperature of thebatch was allowed to rise over a four-hour time period to approximately170° C. At about 80° C., the batch became clear. After an approximatefour-hour hold at 170° to 175° C., the reaction was allowed to coolslowly to room temperature over night. The next morning the reactionmixture was sampled and a 60 percent solution in N-methyl-2-pyrrolidonewas determined to have a viscosity at 25° C. on the Gardner-Holdt scaleof W 1/2. Parts six and seven were then added. The final viscosity ofthe solution at 25° C. was Z on the Gardner-Holdt scale, or 2,500centipoises as measured by a Brookfield RVT Viscometer.

The percent non-volatiles of the solution were determined to be 27percent by baking a two-gram sample for two hours at 200° C. Thespecific gravity of the solution was determined to be 1.025 at 25° C.This solution was then used to overcoat a commercially availablepolyester (ISONEL 200)**. The test properties were as shown in TableOne. It was also coated over a commercially available polyester-imide(ISOMID)*** and tested as shown in Table One.

The temperature of coating the wires in all of the examples was370°-480° C.

EXAMPLE 2

    ______________________________________                                                                 Load                                                 Raw Materials            in Grams                                             ______________________________________                                        (1) N--methyl-2-pyrrolidone                                                                            4168                                                 (2) Toluene diisocyanate (Mondur TD-80)                                                                1033                                                 (3) 4,4-Methylene diphenyldiisocyanate                                                                  637                                                 (4) Terephthalic Acid     494                                                 (5) Dodecanedioic Acid   1267                                                 (6) Xylene               1982                                                 (7) N--methyl-2-pyrrolidone                                                                             910                                                 ______________________________________                                    

The reaction was carried out much in the same fashion as described inExample one, with the exception of the over night cooling step. Thereaction medium was sampled after a three-hour hold at 165° to 180° C.at 60 percent in N-methyl-2-pyrrolidone and found to have a viscosity ofV 1/2 at 25° C. on the Gardner-Holdt Scale. The batch was then reducedwith six and seven to a final viscosity of Y 1/4 at 25° C. on theGardner-Holdt Scale at 28.45 percent non-volatiles determined asdescribed in Example One.

The material was then coated over a polyester (ISONEL 200), a polyesterimide (ISOMID), a polyester overcoated with a polyamide-imide, (ISONEL200 overcoated with trimellitic anhydride-methylene dianiline polymer),a polyamide-imide (trimellitic anhydride-methylene dianiline polymer)wire coating and as a monolithic enamel. The results of the testing onthe coated conductors are as shown in Table one.

EXAMPLES 3 THROUGH 8

Examples Three through Eight describe the effects of the mole percentratio of aliphatic diacid to aromatic diacid. The effects on bondstrength are shown on Graph Number One. (Bond strength versus percentaliphatic diacid). Also shown on Graph Number One is the relationship ofbond strength to breaking temperature. The other properties of thecoated conductors are as displayed in Table One.

The general procedure for making these enamels is as described inExample One.

    ______________________________________                                        Example      3       4      5    6    7    8                                  Reactants    Batch Weight                                                     ______________________________________                                        (1)  N--methyl-2-                                                                              644     611  623  633  655  664                                   pyrrolidone                                                              (2)  Toluene     159     159  159  159  159  159                                   diisocyanate                                                             (3)  4,4'-methylene                                                                             98      98   98   98   98   98                                   diphenyl                                                                      diisocyanate                                                             (4)  Terephthalic                                                                               76     141  118   97   54   32                                   Acid                                                                     (5)  Dodecanedioic                                                                             194     104  135  164  224  254                                   Acid                                                                     (6)  Xylene      327     382  346  331  335  366                              (7)  N--methyl-2-                                                                              119     140  241  140  126  210                                   pyrrolidone                                                              Gardner-Holdt                                                                              Y3/4    X1/2   Y+   Z+   Y1/4 Y                                  Viscosity @ 25° C.                                                     Percent Non- 27.8    24.9   25.2 26.8 23.8 25.7                               Volatiles                                                                     Determined                                                                    2 gm., 2 hr.,                                                                 200° C.                                                                ______________________________________                                    

EXAMPLE 9

This example describes in the use of an aliphatic acid as described inthe disclosure where X equals four.

    ______________________________________                                        Reactants              Batch Weight                                           ______________________________________                                        (1) N--methyl-2-pyrrolidone                                                                          600                                                    (2) Toluene diisocyanate                                                                             171                                                    (3) 4,4' Methylene diphenyldiisocyanate                                                              105                                                    (4) Terephthalic Acid   81                                                    (5) Adipic Acid        133                                                    (6) Xylene             257                                                    Gardner-Holdt Viscosity (25° C.)                                                              W1/2                                                   Determined Percent Non-Volatiles                                                                     32.4                                                   (2 grams, 2 hours, 200° C.)                                            ______________________________________                                         This example was prepared as described in Example One.                        The properties of this enamel when used to overcoat ISOMID are as             described in Table One.                                                  

EXAMPLE 10

This example demonstrates the use of a dibasic acid where X equalseight.

    ______________________________________                                        Reactants              Batch Weight                                           ______________________________________                                        (1) N--methyl-2-pyrrolidone                                                                          560                                                    (2) Toluene diisocyanate                                                                             145                                                    (3) 4,4' Methylene diphenyl diisocyanate                                                              89                                                    (4) Terephthalic Acid   69                                                    (5) Sebacic Acid       156                                                    (6) N--methyl-2-pyrrolidone                                                                          207                                                    (7) Xylene             411                                                    Gardner-Holdt Viscosity (@ 25° C.)                                                            X1/2                                                   Determined percent Non-Volatiles                                                                     24.2                                                   (2 grams, 2 hours, 200° C.)                                            ______________________________________                                         This example was prepared in accordance with the procedure described in       Example One.                                                                  The test results obtained when this enamel was applied over 18AWG copper      wire coated with ISOMID are shown in Table One.                          

EXAMPLE 11

This example indicates that the allowable number of methylene groupsbetween the two carboxyl groups of the aliphatic diacid may not have anupper limit.

    ______________________________________                                        Reactants              Batch Weight                                           ______________________________________                                        (1) N--methyl-2-pyrrolidone                                                                          585                                                    (2) Toluene diisocyanate                                                                              94                                                    (3) 4,4' methylene diphenyl diisocyanate                                                              68                                                    (4) Terephthalic Acid   45                                                    (5) Empol 1010*        283                                                    (6) N--methyl-2-pyrrolidone                                                                          140                                                    (7) Xylene             310                                                    Gardner-Holdt Viscosity (@ 25° C.)                                                            Y1/4                                                   Determined percent Non-Volatiles                                                                     29.4                                                   (2 grams, 2 hours, 200° C.)                                            ______________________________________                                         This reaction was cooked in accordance with the procedure outlined in         Example One.                                                                  The test results obtained when this enamel was applied over 18AWG copper      wire coated with ISOMID are shown in Table One.                               "Empol 1010 is a C.sub.36 dimerized fatty acid available from Emery           Industries, Inc., Cincinnati, Ohio.                                      

EXAMPLE 12

This working example demonstrates the use of a cyclic aliphaticdiisocyanate to replace a portion of the aromatic diisocyanate.

    ______________________________________                                        Reactants            Batch Weight                                             ______________________________________                                        (1) N--methyl-2-pyrrolidone                                                                        600                                                      (2) Toluene diisocyanate                                                                           146                                                      (3) Desmondur W*      97                                                      (4) Dodecanedioic Acid                                                                             179                                                      (5) Terephthalic Acid                                                                               76                                                      (6) N--methyl-2-pyrrolidone                                                                        155                                                      (7) Xylene           323                                                      Gardner-Holdt Viscosity (@ 25° C.)                                                          Z1/4                                                     Determined Percent Non-Volatiles                                                                   27.5                                                     (2 grams, 2 hours, 200° C.)                                            ______________________________________                                         This enamel was prepared as described in Example One. It was then applied     as an overcoat to ISOMID coated copper wire. The test results obtained        from this construction are as shown in Table One.                             *Desmondur W is a cycloaliphatic diisocyanate available from Mobay            Chemical Company, Pittsburgh, Pennsylvania.                              

EXAMPLE 13

This example shows the use of all toluene diisocyanate to make anacceptable bond coat.

    ______________________________________                                        Reactants            Batch Weight                                             ______________________________________                                        (1) N--methyl-2-pyrrolidone                                                                        606                                                      (2) Toluene diisocyanate                                                                           226                                                      (3) Dodecanedioic Acid                                                                             194                                                      (4) Terephthalic Acid                                                                               76                                                      (5) N--methyl-2-pyrrolidone                                                                        210                                                      (6) Xylene           350                                                      Gardner-Holdt Viscosity (@ 25° C.)                                                          X1/4                                                     Determined percent Non-Volatiles                                                                   27.2                                                     (2 grams, 2 hours, 200° C.)                                            ______________________________________                                         This example was prepared using the procedure described in Example One.       However, as indicated no 4,4methylene diphenyl diisocyanate was employed.     When coated over 18AWG ISOMID coated wire, the bond coat gave the             properties as shown in Table One.                                        

COMPARATIVE EXAMPLE 1

A commercial solution of Nylon 66 was coated over a polyester wireenamel, namely, ISONEL 200. The resulting magnet wire exhibited theproperties shown in Table One.

COMPARATIVE EXAMPLE 2

A solution of Nylon 11 was prepared in accordance with U.S. Pat. No.4,216,263 by Otis. The viscosity of this solution was approximatelyZ51/2 on the Gardner-Holdt Scale at 25° C. The percent non-volatiles ofthe solution was determined to be 16.1 percent by baking a two-gramsample for two hours at 200° C. This enamel solution was coated over apolyester-imide of the ISOMID type on AWG-24 copper wire. The electricaland bonding test results are shown in Table One.

COMPARATIVE EXAMPLE 3

A solution of Nylon 11 was prepared in accordance with U.S. Pat. No.4,216,263 by Otis. The viscosity of the solution was approximately Z23/4on the Gardner-Holdt Scale at 25° C. at approximately 16.1 percentnon-volatiles determined as in Example One. This enamel was coated overa polyesterimide wire coating, namely ISOMID on 18-AWG copper wire. Thetest results are shown on Table One. A comparison of the bond strengthof this example to the preferred composition of this disclosure asdescribed by Example One is shown on Graph Number Two.

COMPARATIVE EXAMPLE 4

A solution of Nylon 11 was prepared in accordance with U.S. Pat. No.4,216,263 Otis. The viscosity of this solution was approximately Z31/2on the Gardner-Holdt Scale at 25° C. The percent non-volatilesdetermined as in Example One were 16.8 percent. This enamel was coatedover a polyester wire coating, namely ISONEL 200 on 18-AWG copper wire.The electrical and bonding test results are as shown in Table One.

    ______________________________________                                        Abbreviation Key for Table 1                                                  ______________________________________                                        F. O. M.    Figure of Merit                                                   Hrs.        Hours                                                             FPM         Feet per Minute                                                   VPM         Volts Per Mil                                                     Base Coat:                                                                    PE          Polyester of the ISONEL ® 200 type                            PEI         Polyester-imide of the ISOMID ® type                          PAI         Aromatic polyamide-imide                                          PAI/PE      Polyamide imide based upon                                                    4,4' methylene diphenyl diisocyanate                                          and trimellitic anhydride over-                                               coated over a polyester of the                                                ISONEL ® 200 type                                             None        Indicates the bond coat was applied                                           in eight passes to obtain a three-                                            mil build                                                         Build       total increase in the wire diameter                                           as a result of the coating.                                       Wire Size   All AWG sizes                                                     Speed       The rate the wire traveled as it                                              was coated in multiple passes and                                             in a 15-foot, gas-fired oven.                                     Appearance:                                                                   G           Indicates good or smooth surface.                                 VSW         Indicates smooth surface with a                                               very slight wave.                                                 SW          Indicates minor flaws in the coating                                          surface                                                           Heavy Grain Indicates a rough surface without                                             blisters                                                          Rough       Is an indication the coating is                                               unacceptable as it may contain                                                blisters, or a very heavy grain,                                              or an extreme wave.                                               (+)         Indicates slightly better than given                                          rating                                                            (-)         Indicates slightly worse than given                                           rating                                                            Snap        Measured in accordance with NEMA                                              Standards Publication Part 3,                                                 paragraph 3.1.1.                                                  Mandrel After Snap                                                                        Smallest mandrel around which wire                                            which has been "snapped" as above can be                                      wound without exhibiting surface                                              cracks.                                                           Abrasion    Measured in accordance with NEMA                                  Unilateral  Standard Publication Part 3,                                      Scrape      paragraph 59.1.1.                                                 Windability 1500 volts are passed through a                                               six foot long wire sample which is                                            wrapped around a specified mandrel.                                           The mandrel moves along the wire                                              at fixed rate elongating and                                                  abrading the wire. Failure is                                                 described when three shorts occur                                             along the surface of the sample.                                  Cut Through Measured in accordance with NEMA                                              Standards Publication Part 3,                                                 paragraph 50.1.1.2.                                               Heat Shock  Tested in accordance with NEMA                                                Standards Publication, Part 3,                                                paragraph 4.1.1.                                                  Burn Out    Tested in accordance with NEMA                                                Standards Publication, Part 3,                                                paragraph 53.1.1.4. F.O.M. is                                                 Figure of Merit calculated as                                                 described in NEMA Standards                                                   Publication, Part 3, paragraph                                                53.1.1.3.                                                         A. O. Smith A five-foot sample of wire is                                     Freon Blister                                                                             wound into a coil which produces                                  Test        four to six percent stretch, baked for                                        two hours at 150° C., then cooled                                      to room temperature. The samples                                              are then placed in a freon bomb                                               charged with Freon 22 ® and the                                           pressure in the bomb is brought up                                            to 600 pounds per square inch by                                              heating and held six hours. After                                             the six-hour hold, the pressure is                                            immediately released and coils are                                            placed in an oven at 150° C. for                                       four hours. The coils are then                                                removed from the oven and checked                                             for blistering. One large blister,                                            or two medium, or five small blister                                          constitutes a failure. The wire is                                            then wrapped around a five times                                              mandrel for ten turns and checked                                             for cracks or peeling. If the                                                 coating cracks or peels, it is                                                a failure. Finally, the wire is                                               made into a twisted pair and                                                  dielectrics are determined in                                                 accordance with NEMA Standards                                                Publication, Part 3, paragraph                                                7.1.1.3.                                                          Dielectrics:                                                                  Dry         Determined in accordance with NEMA                                            Standards Publication, Part 3,                                                paragraph 7.1.1.3.                                                Wet         After soaking in water for 24 hours,                                          the samples are tested as described                                           above.                                                            Bonding     Determined following the procedure                                            described in NEMA Standards Publication                                       Part 3, paragraph 57.1.1.2 at the                                             temperature stated under Bonding                                              Temperature.                                                      Dissipation Factor                                                                        Tested in accordance with NEMA                                                Standards Publication, Part 3,                                                Paragraph 9.1.1.2.                                                Heat Aging  Number of hours up to 168 (at 180° C.)                     at 180° C.                                                                         required for a sample to be baked                                             to fail a post winding of around a                                            one times mandrel.                                                ______________________________________                                    

                                      TABLE 1                                     __________________________________________________________________________                    Example        Example                                                        1              2                                              __________________________________________________________________________    Basecoat        PE     PEI     PE      PEI     PEI     PEI                    Build(mils)bondcoat/base-                                                                     1.0/2.0                                                                              1.0/2.0 1.0/2.1 0.9/1.9 1.0/2.0 1.0/2.0                coat                                                                          Wire Size (AWG) 18     18      18      24      24      24                     Wire Speed (fpm)                                                                              50     50      50      100     120     130                    Appearance, bondcoat/base-                                                                    VSW/VSW                                                                              VSW/VSW VSW/VSW+                                                                              VSW/VSW VSW/VSW VSW-/VSW               coat                                                                          MECHANICAL PROPERTIES                                                         Mandrel, before snap                                                                          1X     1X      1X      1X      1X      1X                     Snap (OK or Fail)                                                                             OK     OK      OK      OK      OK      OK                     Mandrel, after snap                                                                           1X     1X      1X      1X      1X      1X                     Abrasion (gms.) 2000+  2000+   1933    1000+   1000+   1000+                  Windability     25     20                                                     Helical Coil Bonding;                                                         Bond Temp., °C.                                                                        200    200             200     200     200                    Bond Str., lbs. @ 25° C.                                                               10.63  16.09           6.6     9.7     9.2                    150° C.  6.40   10.88           4.9     5.2     5.6                    180° C.  3.52   5.87            1.7     0.9     0.8                    200° C.  2.09   2.64            0.4     0.4     0.2                    THERMAL PROPERTIES                                                            Cut Through Temp., °C.                                                                 365    340     355     342     318     316                    Heat Shock, 1X  50     80      70      80      60      70                     (1/2 Hr. at test, 2X                                                                          80     90      80      90      80      80                     temp. 20%, 3X   100    100     100     100     100     100                    pre-stretch), 4X                                                                              100    100     100     100     100     100                    Heat Shock Test Temp., °C.                                                             175    200     175     200     200     200                    Burnout (F.O.M.)                                                                              5.4    6.67                                                   Heat Aging (hrs.)                                                                             168-OK                                                        ELECTRICAL PROPERTIES                                                         Dielectric Strength, dry                                                                      14.6   15.6                                                   (vpm), wet      11.1   11.1                                                   Dissapation Factor                                                                            11.5   4.92            3.34    3.16    5.45                   CHEMICAL PROPERTIES                                                           A. O. Smith Freon Test;                                                                       Fail   OK/OK                                                  appearance/flexibility                                                        dielectric                                                                    __________________________________________________________________________                                            Example                                                                              Example Example                                                        3      4       5                      __________________________________________________________________________    Basecoat        PAI/PE PAI    None None PEI    PEI     PEI                    Build(mils)bondcoat/base-                                                                     1.1/0.7/                                                                             1.0/2.0          1.0/2.0                                                                              1.0/2.0 1.0/2.0                coat            2.3                                                           Wire Size (AWG) 18     18     18   18   18     18      18                     Wire Speed (fpm)                                                                              50     50     40   50   50     50      50                     Appearance, bondcoat/base-                                                                    VSW/VSW/                                                                             VSW/VSW          VSW/VSW                                                                              VSW/VSW VSW/VSW                coat            VSW                                                           MECHANICAL PROPERTIES                                                         Mandrel, before snap                                                                          1X     1X     1X   1X   1X     1X      1X                     Snap (OK or Fail)                                                                             OK     OK     OK   OK   OK     OK      OK                     Mandrel, after snap                                                                           1X     1X     1X   1X   1X     1X      1X                     Abrasion (gms.) 2000+  1816   2000+                                                                              2000+                                                                              1883   1866    1800                   Windability     17     14                                                     Helical Coil Bonding;                                                         Bond Temp., °C.                                                                        200    200    200  200  200    200     200                    Bond Str., lbs. @ 25° C.                                                               19.80  18.65  --   --   21.7   0.4     1.8                    150° C.  --     --     --   --   10.9   0.0     1.0                    180° C.  4.3    3.43   7.4  3.68 6.2    0.0     0.0                    200° C.  --     --     --   --   3.2    0.0     0.0                    THERMAL PROPERTIES                                                            Cut Throught Temp., °C.                                                                385    325    280  260                                        Heat Shock, 1X  80     70     80   80                                         (1/2 Hr. at test, 2X                                                                          90     90     90   90                                         temp. 20%, 3X   100    100    100  100                                        pre-stretch), 4X                                                                              100    100    100  100                                        Heat Shock Test Temp., °C.                                                             260    260    260  260                                        Burnout (F.O.M.)       8.51   2.46 1.13                                       Heat Aging (hrs.)                                                             ELECTRICAL PROPERTIES                                                         Dielectric Strength, dry                                                                      15.9   11.5                                                   (vpm), wet      14.5   11.2                                                   Dissipation Factor                                                                            28.72  22.26  453.0                                                                              1874.0                                     CHEMICAL PROPERTIES                                                           A. O. Smith Freon Test;                                                       appearance/flexibility                                                        dielectric                                                                    __________________________________________________________________________                    Example Example Example Example                                                                             Example  Example                                6       7       8       9     10       11                     __________________________________________________________________________    Basecoat        PEI     PEI     PEI     PEI   PEI      PEI                    Build(mils)bondcoat/base-                                                                     1.0/2.0 1.0/2.0 1.0/2.1 1.0/2.0                                                                             1.0/2.0  1.0/2.1                coat                                                                          Wire Size (AWG) 18      18      18      18    18       18                     Wire Speed (fpm)                                                                              50      50      50      50    50       50                     Appearance, bondcoat/base-                                                                    VSW/VSW VSW/VSW VSW-/VSW                                                                              Wavy/ VSW/VSW+ VSW-/VSW               coat                                    VSW                                   MECHANICAL PROPERTIES                                                         Mandrel, before snap                                                                          1X      1X      1X            1X       1X                     Snap (OK or Fail)                                                                             OK      OK      OK      Fail  OK       OK                     Mandrel, after snap                                                                           1X      1X      1X      --    1X       1X                     Abrasion (gms.) 1950    2000+   1933    --    1808     1708                   Windability                                                                   Helical Coil Bonding;                                                         Bond Temp., °C.                                                                        200     200     200     200   200      200                    Bond Str., lbs. @ 25° C.                                                               2.9     16.2    12.5    --    --       --                     150° C.  2.0     8.0     5.2     --    --       --                     180° C.  1.4     4.7     1.5     0.4   2.8      1.25                   200° C.  1.4     2.2     1.1     --    --       --                     THERMAL PROPERTIES                                                            Cut Through Temp., °C.                                                 Heat Shock, 1X                                                                (1/2 Hr. at test, 2X                                                          temp. 20%, 3X                                                                 pre-stretch), 4X                                                              Heat Shock Test Temp., °C.                                             Burnout (F.O.M.)                                                              Heat Aging (hrs.)                                                             ELECTRICAL PROPERTIES                                                         Dielectric Strength, dry                                                      (vpm), wet                                                                    Dissipation Factor                                                            CHEMICAL PROPERTIES                                                           A. O. Smith Freon Test;                                                       appearance/flexibility                                                        dielectric                                                                    __________________________________________________________________________                                  Compara-      Compara-                                                                            Compara-                                                                            Compara-                              Example                                                                              Example                                                                              tive          tive  tive  tive                                  12     13     Example 1     Example 2                                                                           Example                                                                             Example               __________________________________________________________________________                                                            4                     Basecoat        PEI    PEI    PE    PEI     PEI   PEI   PE                    Build(mils)bondcoat/base-                                                                     1.0/2.1                                                                              1.0/2.1                                                                              1.0/2.0                                                                             1.0/2.0 1.0/2.0                                                                             1.0/2.1                                                                             1.0/2.0               coat                                                                          Wire Size (AWG) 18     18     18    18      24    18    18                    Wire Speed (fpm)                                                                              50     50     50    50      90    50    50                    Appearance, bondcoat/base-                                                                    SW/VSW Hvy,   VSW-/ VSW-/VSW                                                                              SW/VSW                                                                              VSW-/ SW/VSW                coat                   Grain/VSW                                                                            VSW                 VSW                         MECHANICAL PROPERTIES                                                         Mandrel, before snap                                                                          1X     1X     1X    1X      1X    1X    1X                    Snap (OK or Fail)                                                                             OK     OK     OK    OK      OK    OK    OK                    Mandrel, after snap                                                                           1X     1X     1X    1X      1X    1X    1X                    Abrasion (gms.) 1950   2000+  2000+ 1916    1000+ 1750  1608                  Windability                                                                   Helical Coil Bonding;                                                         Bond Temp., °C.                                                                        200    200    200   200     200   200   200                   Bond Str., lbs. @ 25° C.                                                               --     --     0.0   0.0     4.7   22.4  21.7                  150° C.  --     --     --    --      0.8   11.0                        180° C.  6.3    5.5    0.0   0.0     0.2   2.8                         200° C.  --     --     --    --      --    0.4                         THERMAL PROPERTIES                                                            Cut Through Temp., °C. 280   285     334   315   395                   Heat Shock, 1X                80    90      50    90    20                    (1/2 Hr. at test, 2X          90    100     70    100   30                    Temp. 20%, 3X                 100   100     80    100   40                    pre-stretch), 4X              100   100     100   100   40                    Heat Shock Test Temp., °C.                                                                           175   200     200   175   175                   Burnout (F.O.M.)                                  5.97  5.46                  Heat Aging (hrs.)                                                             ELECTRICAL PROPERTIES                                                         Dielectric Strength, dry                          11.1                        (vpm), wet                                                                    Dissipation Factor                                                            CHEMICAL PROPERTIES                                                           A. O. Smith Freon Test;                                                       appearance/flexibility                                                        dielectric                                                                    __________________________________________________________________________

It is critical to use terephthalic acid in copolyamides of theinvention. Thus if in place of terephthalic acid there is usedisophthalic acid in whole or in part as taught by Onder U.S. Pat. No.4,072,665, the bond strength is reduced.

Thus there were prepared copolyamides similar to Example 1 replacing theterephthalic acid in whole or in part by isophthalic acid.

COMPARATIVE EXAMPLE 5

The procedure was similar to Example 1 but there were used as reactantsa 70/30 molar ratio mixture of toluene diisocyanate and methylenediisocyanate and there was used a 65/25/10 molar mixture ofdodecanedioic acid, isophthalic acid and terephthalic acid.

COMPARATIVE EXAMPLE 6

The procedure was the same as in Comparative Example 5 except thedibasic acids employed was 65/35 molar mixture of dodecanedioic acid andisophthalic acid.

Examples 1 and 3 which are within the present invention both employ a65/35 molar mixture of dodecanedioic acid and terephthalic acid. Thebond strength of Comparative Example 5, Comparative Example 6, Example1, and Example 3 were tested by coating their resultant enamel solutionson top of ISOMID-coated wire at 50 ft./min., followed by bonding at 200°C. for 20 minutes under 1-kg load. The results were as set forth inTable 2:

                  TABLE 2                                                         ______________________________________                                        Test              Bond Strength,                                              Specimen          Lbs. at 180° C.                                      ______________________________________                                        Comparative Example 5                                                                           4.75                                                        Comparative Example 6                                                                           3.2                                                         Example 1         5.9                                                         Example 3         6.2                                                         ______________________________________                                    

It can be seen from Table 2 that the greater the replacement ofterephthalic acid by isophthalic acid the greater the reduction in bondstrength.

What is claimed is:
 1. A self bondable copolyamide having the recurringunit ##STR4## where AL is the divalent hydrocarbon residue of anunsubstituted aliphatic dicarboxylic acid having at least 6 carbonatoms, R is tolylene, phenylene, ##STR5## where F is O, CH₂, or SO₂, Aris p-phenylene, y is 35 to 80% of the recurring units and z is 65 to 20%of the recurring units.
 2. A copolyamide according to claim 1 where y is35 to 70% of the recurring units.
 3. A copolyamide according to claim 2where y is 40 to 70% of the recurring units.
 4. A copolyamide accordingto claim 3 where y is 60 to 70% of the recurring units.
 5. A copolyamideaccording to claim 4 where y is about 65% of the recurring units.
 6. Acopolyamide according to claim 1 where R is tolylene, 4,4'-methylenediphenylene or a mixture thereof.
 7. A copolyamide according to claim 6where R has the mole percent ratio of 4-methyl-m-phenylene,2-methyl-m-phenylene, 4,4'-methylene diphenylene of 40/10/50 to 80/20/0.8. A copolyamide according to claim 4 where R has the mole percent ratioof 4-methyl-m-phenylene, 2-methyl-m-phenylene, 4,4'-methylenediphenylene of 40/10/50 to 80/20/0.
 9. A copolyamide according to claim1 where AL is (CH₂)_(x) where x is 4 to
 34. 10. A copolyamide accordingto claim 9 where y is 35 to 70% of the recurring units.
 11. Acopolyamide according to claim 10 where y is 40 to 70% of the recurringunits.
 12. A copolyamide according to claim 11 where y is 60 to 70% ofthe recurring units.
 13. A copolyamide according to claim 12 where y isabout 65% of the recurring units.
 14. A copolyamide according to claim13 where R is tolylene, 4,4'-methylene diphenylene or a mixture thereof.15. A copolyamide according to claim 14 where R has the mole percentratio of 4-methyl-m-phenylene, 2-methyl-m-phenylene, 4,4'-methylenediphenylene of 40/10/50 to 80/20/0.
 16. A copolyamide according to claim12 where R has the mole percent ratio of 4-methyl-m-phenylene,2-methyl-m-phenylene, 4,4'-methylene diphenylene of 40/10/50 to 80/20/0.17. A copolyamide according to claim 9 where x is 6 to
 12. 18. Acopolyamide according to claim 17 where y is 35 to 70% of the recurringunits.
 19. A copolyamide according to claim 18 where y is 40 to 70% ofthe recurring units.
 20. A copolymer according to claim 19 where y is 60to 70% of the recurring units.
 21. A copolyamide according to claim 20where y is about 65% of the recurring units.
 22. A copolymer accordingto claim 21 where R is tolylene, 4,4'-methylene diphenylene or a mixturethereof.
 23. A copolyamide according to claim 22 where R has the molepercent ratio of 4-methyl-m-phenylene, 2-methyl-m-phenylene,4,4'-methylene diphenylene of 40/10/50 to 80/20/0.
 24. A copolyamideaccording to claim 20 where R has the mole percent ratio of4-methyl-m-phenylene, 2-methyl-m-phenylene, 4,4'-methylene diphenyleneof 40/10/50 to 80/20/0.
 25. A copolyamide according to claim 17 where xis
 10. 26. A copolyamide according to claim 25 where y is 35 to 70% ofthe recurring units.
 27. A copolyamide according to claim 26 where y is40 to 70% of the recurring units.
 28. A copolymer according to claim 27where y is 60 to 70% of the recurring units.
 29. A copolyamide accordingto claim 28 where y is about 65% of the recurring units.
 30. A copolymeraccording to claim 29 where R is tolylene, 4,4'-methylene diphenylene ora mixture thereof.
 31. A copolyamide according to claim 30 where R hasthe mole percent ratio of 4-methyl-m-phenylene, 2-methyl-m-phenylene,4,4'-methylene diphenylene of 40/10/50 to 80/20/0.
 32. A copolyamideaccording to claim 28 where R has the mole percent ratio of4-methyl-m-phenylene, 2-methyl-m-phenylene, 4,4'-methylene diphenyleneof 40/10/50 to 80/20/0.
 33. An enamel comprising the copolyamide ofclaim 1 dissolved in a solvent.
 34. An enamel comprising the copolyamideof claim 2 dissolved in a solvent.
 35. An enamel comprising thecopolyamide of claim 3 dissolved in a solvent.
 36. An enamel comprisingthe copolyamide of claim 4 dissolved in a solvent.
 37. An enamelcomprising the copolyamide of claim 5 dissolved in a solvent.
 38. Anenamel comprising the copolyamide of claim 6 dissolved in a solvent. 39.An enamel comprising the copolyamide of claim 7 dissolved in a solvent.40. An enamel comprising the copolyamide of claim 8 dissolved in asolvent.
 41. An enamel comprising the copolyamide of claim 9 dissolvedin a solvent.
 42. An enamel comprising the copolyamide of claim 10dissolved in a solvent.
 43. An enamel comprising the copolyamide ofclaim 11 dissolved in a solvent.
 44. An enamel comprising thecopolyamide of claim 12 dissolved in a solvent.
 45. An enamel comprisingthe copolyamide of claim 13 dissolved in a solvent.
 46. An enamelcomprising the copolyamide of claim 14 dissolved in a solvent.
 47. Anenamel comprising the copolyamide of claim 15 dissolved in a solvent.48. An enamel comprising the copolyamide of claim 16 dissolved in asolvent.
 49. An enamel comprising the copolyamide of claim 17 dissolvedin a solvent.
 50. An enamel comprising the copolyamide of claim 18dissolved in a solvent.
 51. An enamel comprising the copolyamide ofclaim 19 dissolved in a solvent.
 52. An enamel comprising thecopolyamide of claim 20 dissolved in a solvent.
 53. An enamel comprisingthe copolyamide of claim 21 dissolved in a solvent.
 54. An enamelcomprising the copolyamide of claim 22 dissolved in a solvent.
 55. Anenamel comprising the copolyamide of claim 23 dissolved in a solvent.56. An enamel comprising the copolyamide of claim 24 dissolved in asolvent.
 57. An enamel comprising the copolyamide of claim 25 dissolvedin a solvent.
 58. An enamel comprising the copolyamide of claim 26dissolved in a solvent.
 59. An enamel comprising the copolyamide ofclaim 27 dissolved in a solvent.
 60. An enamel comprising thecopolyamide of claim 28 dissolved in a solvent.
 61. An enamel comprisingthe copolyamide of claim 29 dissolved in a solvent.
 62. An enamelcomprising the copolyamide of claim 30 dissolved in a solvent.
 63. Anenamel comprising the copolyamide of claim 31 dissolved in a solvent.64. An enamel comprising the copolyamide of claim 32 dissolved in asolvent.